Is it possible to declare a wildcard statement in OSM relations to enable any substring references that start with eg. “GR” to be true (ie GR1, GR2, GR5) .
type=route & route=hiking & ref=GR* { apply {add my_tagGR=yes} } does not work.
It is a normal regular expression way. Dot means “any character” and * means “zero or more times”. Your original expression should find strings “GR”, “GRR”, GRRR", “GRRRR” etc.